With the fast development of display technology, touch screen panels have become popular in people's life gradually. At present, according to constitution structures, touch screens may be classified into add-on mode touch panels, on-cell touch panels and in-cell touch panels. For an add-on mode touch panel, the touch panel and the liquid crystal display (LCD) are produced separately and then attached together to form a liquid crystal display with touch function. Add-on mode touch panels suffer disadvantages such as high manufacturing cost, low light transmission rate and thick assembly. For an in-cell touch panel, touch electrodes of the touch panel are embedded inside the liquid crystal display, which can reduce the overall thickness of the module, and can drastically reduce manufacturing cost of the touch panel. Therefore, in-cell touch panels have received good graces from panel manufacturers.
At present, a capacitive in-cell touch panel is implemented by directly adding touch driving electrodes and touch sensing electrodes on a TFT (Thin Film Transistor) array substrate, that is, manufacturing two layers of strip ITO (Indium Tin Oxide) electrodes intersecting each other on different planes on the TFT array substrate, which functions as touch driving electrodes and touch sensing electrodes respectively. As shown in FIG. 1, transversely arranged touch driving electrodes Tx and longitudinally arranged touch sensing electrodes Rx couple with each other to generate mutual capacitance Cm. When a finger touches the screen, the touch action can change the value of mutual capacitance Cm. The touch detection device can detect position of the touch point of the finger by detecting variation amount of electric current corresponding to capacitance Cm before and after the touch action.
Two kinds of mutual capacitances Cm are formed between transversely arranged touch driving electrodes Tx and longitudinally arranged touch sensing electrodes Rx. As shown in FIG. 1, one kind is the projection capacitance effective for implementing touch function (as shown by arrowed curve line in FIG. 1). When a finger touches the screen, the projection capacitance value may be changed. Another kind is the direct opposing capacitance non-effective for implementing touch function (as shown by the arrowed straight line). When a finger touches the screen, the direct opposing capacitance value would not bed changed.